Systems and methods for correcting spinal deformities

ABSTRACT

The present invention relates generally to medical devices and methods generally aimed at spinal surgery. In particular, the disclosed system and associated methods relate to performing spinal fixation with the use of a deformity system.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/543,892 filed Aug. 19, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/359,365 filed Nov. 22, 2016, now U.S. Pat. No.10,456,173, which is a continuation of U.S. patent application Ser. No.14/667,619 filed Mar. 24, 2015, now U.S. Pat. No. 9,572,599, which is acontinuation of U.S. patent application Ser. No. 12/945,821 filed Nov.12, 2010, now U.S. Pat. No. 8,986,349, which claims the benefit ofpriority from U.S. provisional patent application No. 61/260,357 filedNov. 11, 2009, and U.S. provisional patent application No. 61/390,561filed Oct. 6, 2010, the entire contents of which are hereby expresslyincorporated by reference into this disclosure as if set forth in theirentireties herein.

FIELD

The present invention relates generally to medical devices and methodsgenerally aimed at spinal surgery. In particular, the disclosed systemand associated methods relate to performing spinal fixation with the useof a deformity system.

BACKGROUND

The spine is formed of a column of vertebra that extends between thecranium and pelvis. The three major sections of the spine are known asthe cervical, thoracic and lumbar regions. There are 7 cervicalvertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae, with each ofthe 24 vertebrae being separated from each other by an intervertebraldisc. A series of about 9 fused vertebrae extend from the lumbar regionof the spine and make up the sacral and coccygeal regions of thevertebral column.

The main functions of the spine are to provide skeletal support andprotect the spinal cord. Even slight disruptions to either theintervertebral discs or vertebrae can result in serious discomfort dueto compression of nerve fibers either within the spinal cord orextending from the spinal cord. If a disruption to the spine becomessevere enough, damage to a nerve or part of the spinal cord may occurand can result in partial to total loss of bodily functions (e.g.,walking, talking, and breathing, etc.). Therefore, it is of greatinterest and concern to be able to both correct and prevent any ailmentsof the spine.

Fixation systems are often surgically implanted into a patient to aid inthe stabilization of a damaged spine or to aid in the correction ofother spinal geometric deformities. Spinal fixation systems are oftenconstructed as framework stabilizing a particular section of the spine.Existing systems often use a combination of rods, plates, pedicle screwsand bone hooks for fixing the framework to the affected vertebrae. Theconfiguration required for each patient varies due to the patient'sspecific anatomical characteristics and ailments. As a result, there isa need for a modular spinal fixation system that allows for a largedegree of custom configurations and that can assist the clinician in thecorrective maneuvers often needed to rehabilitate severe deformities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a spinal anchor assembly according toone example embodiment;

FIG. 2 is an exploded view of the spinal anchor assembly of FIG. 1 ;

FIG. 3 is a partial cross section view of the spinal anchor assembly ofFIG. 1 ;

FIG. 4 is a perspective view of the receiver forming a part of thespinal anchor assembly of FIG. 1 ;

FIG. 5 is a top view of one example of a closure structure;

FIG. 6 is a perspective view of the closure structure of FIG. 5 ;

FIG. 7 is a perspective cross section view of the closure structure ofFIG. 5 ;

FIG. 8 is a perspective view of a collet forming part of the receiverassembly of FIG. 1 ;

FIG. 9 is a top view of the collet forming part of the receiver assemblyof FIG. 1 ;

FIG. 10 is side view of the collet forming part of the receiver assemblyof FIG. 1 ;

FIG. 11 is a perspective view of another spinal anchor assemblyaccording to a second example embodiment;

FIG. 12 is a partial cross section view of the spinal anchor assembly ofFIG. 11 ;

FIG. 13 is an exploded view of the spinal anchor assembly of FIG. 11 ;

FIG. 14 is a perspective view of the receiver forming a part of thespinal anchor assembly of FIG. 11 ;

FIG. 15 is a top view of the collar forming part of the receiverassembly of FIG. 11 ;

FIG. 16 is a perspective view of the collar of FIG. 15 ;

FIG. 17 a top view of the cradle forming part of the receiver assemblyof FIG. 11 ;

FIG. 18 is a perspective view of the cradle of FIG. 17 ;

FIG. 19 is a perspective view of an another anchor assembly according toa third example embodiment of the present disclosure;

FIG. 20 is an exploded view of the anchor assembly of FIG. 19 ;

FIG. 21 is a perspective view of the bone screw forming part of ananchor assembly of FIG. 19 ;

FIG. 22 is a perspective view of the bone screw of FIG. 21 forming partof an anchor assembly of FIG. 10 ;

FIG. 23 is a perspective view of a receiver forming a part of the anchorassembly of FIG. 19 ;

FIG. 24 is a perspective view of one example collar forming part of theanchor assembly of FIG. 19 ;

FIG. 25 is a perspective view of another example collar forming part ofthe anchor assembly of FIG. 19 ;

FIG. 26 is a partial cross section view of the collar of FIG. 24 ;

FIG. 27 is a partial cross section view of the collar of FIG. 25 ;

FIG. 28 is a top view of the collar of FIG. 24 ;

FIG. 29 is a top view of the collar of FIG. 25 ;

FIG. 30 is a partial cross section view of the anchor assembly of FIG.19 ;

FIG. 31 is a perspective view of a partial cross section view of aspinal anchor assembly according to a fourth embodiment of the presentdisclosure;

FIG. 31 is a perspective view of another spinal anchor assembly,according to a fourth example embodiment of the present disclosure;

FIG. 32 is a partial cross section view of the spinal anchor assembly ofFIG. 31 ;

FIG. 33 is a partial cross section view of the spinal anchor assembly inan unlocked position, according to a fifth embodiment of the presentdisclosure;

FIG. 34 is a partial cross section view of the spinal anchor assembly ofFIG. 33 in the locked position;

FIG. 35 is a perspective view of the loading ring of FIG. 33 ;

FIG. 36 is a perspective view of the collet of FIG. 33 ;

FIG. 37 is a partial cross section view of a spinal anchor assembly inan unlocked position according to the sixth embodiment of the presentinvention;

FIG. 38 is a partial cross section view of the spinal anchor assembly ofFIG. 37 in the locked position;

FIG. 39 is a perspective view of the split ring of FIG. 37 ;

FIG. 40 is a perspective view of the loading ring of FIG. 37 ;

FIG. 41 is a perspective view of one example of a spinal anchorassembly, according to a seventh embodiment of the present invention;

FIG. 42 is a partial cross section view of the spinal anchor assembly ofFIG. 41 ;

FIG. 43 is a perspective view of one an arched transverse connectoraccording to one example embodiment;

FIG. 44 is a top view of an arched transverse connector of FIG. 43 ;

FIG. 45 is a side view of an arched transverse connector of FIG. 43 ;

FIG. 46 is a partial section view of an arched transverse connector ofFIG. 43 ;

FIG. 47 is a perspective view of an eccentric pin of the archedtransverse connector of FIG. 43 ;

FIG. 48 is a side view of an eccentric pin of the arched transverseconnector of FIG. 43 ;

FIG. 49 is a perspective view of an arched transverse connectoraccording to a second example embodiment;

FIG. 50 is a cross section view of the arched transverse connector ofFIG. 49 ;

FIG. 51 is a side view of an arched transverse connector according to athird example embodiment of the present invention;

FIG. 52 is a cross section view of arched transverse connector of FIG.51 ;

FIG. 53 is an exploded view of the arched transverse connector of FIG.51 ;

FIG. 54 is a perspective view of a slide arm of the arched transverseconnector of FIG. 51 ;

FIG. 55 is a perspective view of a securing block of the archedtransverse connector of FIG. 51 ;

FIG. 56 is a perspective view of a reduction tower, according to anexample embodiment;

FIG. 57 is a cross section view of the reduction tower of FIG. 56 ;

FIG. 58 is a perspective view of a locking tool according to one exampleembodiment for use with the spinal anchor assembly of FIG. 1 ;

FIG. 59 is another perspective view of the locking tool of FIG. 58 ;

FIG. 60 is a perspective view of one example of a tooling assembly,according to a first embodiment of the present invention;

FIG. 61 is a cross section view of a tooling assembly of FIG. 60 ;

FIG. 62 is a partial cross section view of a tooling assembly of FIG. 60;

FIG. 63 is a perspective section view of one example of a reductiontower grasping a spinal anchor assembly and reducing a rod;

FIG. 64 is a perspective partial section view of one example of areduction tower grasping a spinal anchor assembly and reducing a rod;

FIG. 65 is a perspective view of one example of a reduction tower,according to a second embodiment of the present invention;

FIG. 66 is a cross section view of the reduction tower of FIG. 65 ;

FIG. 67 is a perspective view of the reduction tower link in the openposition;

FIG. 68 is an exploded perspective view of the reduction tower link ofFIG. 67 ;

FIG. 69 is a detailed view of the ratcheting mechanism of the reductiontower link of FIG. 67 ;

FIG. 70 is a detailed view of the ratcheting mechanism with the outerand inner cylinders of FIG. 67 removed;

FIG. 71 is a perspective view of the reduction tower link of FIG. 67with arrows indicating the direction of movement when the arms aresqueezed together; and

FIG. 72 is an exemplary configuration of a deformity spinal fixationassembly.

DETAILED DESCRIPTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as a compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure. The spinal anchor assembly disclosed herein boasts avariety of inventive features and components that warrant patentprotection, both individually and in combination.

FIG. 1 illustrates an example of a spinal anchor assembly 10 accordingto a first embodiment of the present invention. The spinal anchorassembly 10 includes a bone screw 11 and a receiver assembly 12. Aclosure structure 13 (shown in FIGS. 5-7 ) is used to capture a rodwithin the receiver assembly 12. The spinal anchor assembly 10 andclosure structure 13 are composed of a metal (e.g., titanium, stainlesssteel, etc.).

The bone screw 11 of the present invention is configured to attachsecurely within a bony structure (e.g., pedicle of a vertebra) and toallow the receiver assembly 12 to provisionally lock into positionrelative to the bone screw 11 after placement of the bone screw 11within a bony structure. The receiver assembly 12 and bone screw 11 areconfigured to engage with full polyaxial motion. The receiver assembly12 and bone screw 11 can also be provisionally locked (that is, fixedrelative to each other prior to final capture and locking of a spinalrod into the receiver), as will be described in more detail below. Thisversatile engagement between the receiver assembly 12 and bone screw 11provides both the ease of positioning and rod placement associated withpolyaxial screws and the ability to leverage the bone anchor 10 tomanipulate the vertebral body (e.g., parallel distraction andcompression and/or vertebral body derotation) associated with fixed-axisanchors.

By way of example, the bone screw 11 of the spinal anchor assembly 10may be engaged within a pedicle of a vertebra and aligned with a spinalrod connecting other anchors. A clinician may then engage an instrumentto the receiver assembly 12 and provisionally lock the screw 11 andreceiver 12. With the screw locked, the clinician can utilize theinstrument to apply a force upon the vertebra to correct the deformityprior to fixing the construct and thus the spinal column in a desiredposition. The ability to utilize the spinal anchor assembly 10 toreposition segments of the spine to correct deformities simplifies theprocedure for the clinician by limiting the amount of tools and timerequired.

With reference to FIGS. 1-3 , the bone screw 11 of the spinal anchorassembly 10 is comprised of a shank 17, a body 8, and a capturestructure 16. At least one helically-wound bone implantable thread 18extends radially from the body 8 and functions to secure the placementof the bone screw 11 within a bony structure. The capture structure 16includes at least one tool engaging feature 14 that can be used, forexample, to engage and attach various tooling for aligning and advancingthe bone screw 11 into a bony structure. The generally spherical shapeof the capture structure 16 allows it, for example, to articulate withinthe collet 40 to achieve the polyaxial motion between the bone screw 11and the receiver assembly 12. The surface of the capture structure 16may be textured (e.g., scored or knurled) for enhancing frictionalengagement with the collet 40 that secures the positioning of the bonescrew 11 relative to the receiver assembly 12.

The receiver assembly 12 is configured to receive an elongate structure(e.g., a rod) and the closure structure 13 is designed to secure the rodwithin the receiver assembly 12. Once the receiver assembly 12 and bonescrew 11 are securely oriented in the desired orientation and the rod iscaptured in the receiver assembly 12, the closure structure 13 canengaged to lock the rod in the receiver assembly 12.

The receiver assembly 12 is typically provided in an assembled state(best shown in FIG. 3 ) and includes a receiver 20 and a retaining andarticulating structure or collet 40. The receiver 20 has a generallyU-shaped appearance with a generally cylindrical inner profile and afaceted outer profile. A base 26, with a pair of upstanding arms 29forms a U-shaped cradle which define U-shaped openings 27 through thefaceted sides of the receiver 20.

Receivers may be provided in a variety of dimensions depending on thesize and shape of the rod that it will be in secured frictionalengagement with.

Both arms 29 have at least one helically-wound guide and advancementstructure 25 at least partially situated along their internal wallsbeginning from the top surface 28 end of the receiver 20. The guide andadvancement structure 25 of the receiver 20 are configured to mate withat least one exterior helically-wound guide and advancement structure 72of the closure structure 13. When the internal and external guide andadvancement structures 25, 72 of the closure structure 13 and receiver20 are interlocked, their connection prevents the arms 29 of thereceiver 20 from spreading open due to the mating features of the guideand advancement structures 25 and 72. This interlocked configurationprevents splaying of the arms 29.

As illustrated in FIG. 4 , the outer surface of the receiver 20 includestooling attachment features, such as grip bores 21, on the outer surfaceof both arms 29 which function to allow a variety of tools to engage thereceiver assembly 12 for subsequent positioning and implantation of thespinal anchor assembly 10. Additional features of the receiver 20include two sweeping steps 38 recessed inwardly from the inside walls ofthe arms 29 (with one sweeping step 38 situated on each arm 29). Thesweeping steps 38 are utilized during the assembly of the receiverassembly 12 by allowing the locking ledges 55 of the collet 40 to beguided into position within the receiver 20. Once the collet 40 isassembled within the receiver 20, the collet 40 is allowed limitedmovement. By way of example, each sweeping step 38 includes a notch 39that prevents the locking ledge 55 from backing out of the sweeping step38 once it has traveled past the notch 39. Additionally, the top andbottom walls of each sweeping step 38 restricts the longitudinaltranslation of the collet 40 relative to the receiver by restricting thelongitudinal translation of the locking ledge to only between the topand bottom walls of the sweeping step 38. By way of example only, eachsweeping step 38 spans at least a portion of the inside wall of an arm29 and are positioned generally 180 degrees apart from one another.

Located within the base 26 of the receiver 20 is a tapered cavity 34that is sized and shaped for slidable mating and eventual frictionalengagement with the tapered feature 48 of the collet 40, as will bedescribed in more detail below. By way of example only, the taperedcavity 34 may have a taper of approximately 2-3 degrees (shown as angleY in FIG. 3 ). The taper feature 48 of the collet 40 is shown as angle Zin FIG. 10 . When the collet 40 is forced generally in the direction ofthe base 26 of the receiver 20 along its longitudinal axis, the taperedfeature 48 of the collet will become frictionally secured (wedged)within the tapered cavity 34.

FIGS. 8-10 illustrate an example of a collet 40 according to a firstembodiment. The collet 40 includes a top surface 41, a bottom surface42, an inner spherical surface 49, a tapered feature 48, locking ledges55, a saddle 46, and a tooling engagement feature 52. Notably, thecollet 40 is not continuous, and instead includes a slot 44. The slot 44is dimensioned to be a distance X (best shown in FIG. 9 ) and allows thecollet 40 to be temporarily expanded or compressed to receive thecapture structure 16 and to secure the capture structure 16 within theinner spherical surface 49.

During assembly of the spinal anchor assembly 10, the collet 40receives, and permanently captures, the capture structure 16 within theinner spherical surface 49. Once the capture structure 16 is capturedwithin the inner spherical surface 49, the collet 40 and associated bonescrew 11 is assembled to the receiver 20. This is accomplished byleading the distal end of the bone screw 11 through the center of thereceiver until the locking ledges 55 are aligned with the sweeping step38 of the receiver 20. As described above, the locking ledges 55 travelalong the sweeping steps 38 until they pass the notch 39, where thecollet 40 then becomes permanently limited in movement relative to thereceiver 20. At this point, the collet 40 is able to travel a limiteddistance along its longitudinal axis. Additionally, the bone screw 11 isable to articulate relative to the receiver assembly 12 achieve polyaxial motion of the receiver assembly. By way of example, the bone screw11 is able to articulate and form an angle between its longitudinal axisand the longitudinal axis of the receiver 20 of up to approximately 20degrees in any direction. When the desired angular orientation isachieved, the receiver assembly 12 is locked into position relative tothe bone screw 11. For this to occur, the collet 40 is wedged into thereceiver 20 which compresses the slot 44 and causes the inner sphericalsurface 49 to frictionally engage and secure the capture structure 16.This permanently fixes the configuration of the receiver 20, collet 40,and bone screw 11.

As discussed, the anchor assembly 10 can be both provisionally lockedand finally locked. By way of a first example, the spinal anchorassembly 10 can be finally locked by driving a rod (e.g., rod 60) intothe collet 40 and receiver 20 by engaging and advancing a closurestructure 13 into the receiver 20. As the closure structure 13 advances,the rod is forced down into the collet 40 and the collet 40 in turn isdriven down and wedges into the tapered cavity 34. At this point, thecollet 40 is locked into position relative to the receiver 20 and therod is securely locked between the closure structure 13 and collet 40.

The spinal anchor assembly 10 can be provisionally locked by fullyreducing the rod 60) into the collet 40 and receiver 20 with aninstrument, such as the reduction tower 900 (described below). Thereduction tower 900 releasably attaches to the receiver 20 and an armdirects the rod 60 into the receiver 20, forcing the rod into the collet40 which is driven down and wedges into the tapered cavity 34. At thispoint, the collet 40, receiver 20, and bone screw 11 are locked intoposition relative to each other, however, the rod is not locked withinthe receiver assembly 12, and the bone anchor can be used to adjust theposition or orientation of the vertebra to which the anchor assembly 10is attached (e.g., parallel distraction and compression or derotation).The closure structure 13 can be advanced into the receiver 20 when itbecomes desirable to secure the rod within the receiver assembly 12.

By way of another example, the spinal anchor assembly 10 can beprovisionally locked by driving a rod-like tooling feature into the rodinto the collet 40. Again, this provisional locking feature provides aplatform for the clinician to utilize the screw to manipulate theposition or orientation of the vertebra while still allowing thereceiver to be adjusted for easier reception of the rod. The toolingengagement features 52 of the collet 40 allow the user to unlock theanchor assembly 10 from the provisionally locked configuration, ifnecessary. A tool can engage the tooling engagement features 52 to, forexample, compress and/or pull on the collet 40 in order to release thefrictional engagement between the tapered feature 48 of the collet 40and tapered cavity 34 of the receiver 20.

The saddle 46 of the collet 40 provides a contouring surface for matingwith a rod within the receiver assembly 12. By way of example only (andbest shown in FIG. 8 ), the saddle 46 has two U-shaped surfaces that aregenerally shaped to receive a rod. The saddle 46 may be any number ofshapes and sizes necessary to accommodate a particular rod, withoutdeparting from the scope of this invention. Furthermore, the shape anddimensions of the collet 40 and its features may be any number of shapesand dimensions without departing from the scope of this invention.

FIGS. 5-7 illustrate one example embodiment of a closure structure 13.The closure structure 13 is shown by way of example to include a topsurface 70, a base 71, and at least one exterior guide and advancementstructure 72. The top surface 70 includes at least one generallyrecessed tool engaging feature 73 which functions to engage a variety oftooling that assist in aligning and securing the closure structure 13 tothe receiver assembly 12. A recessed slot 75 on the top surface 70functions to provide the clinician with an aligning mechanism forscrewing the closure structure 13 into the receiver 20. For example, therecessed slot 75 of the closure structure 13 should be aligned with therecessed slot 24 of the receiver 20 prior to advancing the closurestructure 13 to facilitate proper engagement. Positioned centrallywithin the base 71 of the closure structure 13 is a point force feature74 that applies a point force to secure a portion of a rod (e.g., rod60). The point force feature 74 deforms upon final tightening of thescrew and improves resistance to translation and centers the lockingstress within the receiver 12. It will be appreciated that while theclosure structure 13 shown may be preferred, closure structuresutilizing a number of other suitable structures and features may beutilized without departing from the scope of this invention.

FIG. 11 illustrates an example of a spinal anchor assembly 100 accordingto a second embodiment of the present invention. The spinal anchorassembly 100 includes a bone screw 111 and a receiver assembly 112. Byway of one example, a closure structure 13 (shown in FIGS. 5-7 ) is usedto capture a rod within the receiver assembly 112. The spinal anchorassembly 100 is preferably composed of a metal (e.g., titanium,stainless steel, etc.).

The spinal anchor assembly 100 of the present invention is available toa clinician in a pre-assembled state such that the receiver assembly 112is jointly attached to the capture structure 116 of the bone screw 111.The receiver assembly 112 and bone screw 111 are able configured toengage with limited axial movement. More specifically, the receivermember 112 may articulate along a single plane (i.e., uniplanarmovement), and can ultimately be secured at any number of angles withinthe single plane. Similar to the provisional locking anchor assembly 10,the uniplanar engagement between the receiver assembly 112 and the bonescrew 111 permits some flexibility for positioning the rod, while stillproviding the ability to leverage the anchor assembly to manipulate thevertebra to correct positioning and alignment of the vertebra. By way ofexample, the anchor assembly may be implanted such that the articulatingplane is the sagittal plane (i.e., movement is cranial-caudal).Positioned as such, force may be applied to the screw in the transverseplane (i.e., medial/lateral direction) to derotate a vertebra. Oneadvantage of limiting the angled articulation between the receiverassembly 112 and bone screw 111 to only along a single plane is so thatforce can be applied upon the spinal anchor assembly 100 in anydirection that is along a non-articulating plane. By way of example, thebone screw 111 of the spinal anchor assembly 100 would be first securedwithin a pedicle of a vertebra. A clinician may engage an instrument tothe receiver assembly 112 and to apply the correcting force.

With reference to FIGS. 11-13 , the spinal anchor assembly 100 iscomprised of a shank 117, a body 108, and a capture structure 116. Atleast one helically-wound bone implantable thread 118 extends radiallyfrom the body 108 and functions to secure the placement of the bonescrew 111 within a bony structure. Additionally, the capture structure116 includes flat surfaces 119 on opposing sides of the capturestructure 116. The flat surfaces 119 restrict rotation between the bonescrew 111 and the collar 140 to the plane parallel to the flat side 19.Preferably, the articulating plane is aligned with the side openings 127such the uniplanar movement is in line with the rod.

The capture structure 116 includes at least one tool engaging feature114 that can be used, for example, to engage and attach various toolingfor aligning and advancing the bone screw 111 into a bony structure. Thegenerally spherical shape portions of the capture structure 116 allowthe capture structure 116, for example, to articulate within the collar140 along a single plane. The surface of the capture structure 116 maybe textured (e.g., scored or knurled) for enhancing frictionalengagement with the collar 140, which assists in securing the positionof the bone screw 111 relative to the receiver assembly 112, as will bediscussed in more detail below.

FIG. 12 illustrates an example embodiment of a receiver assembly 112.The receiver assembly 112 is typically provided in an assembled state(as shown in FIGS. 11 and 12 ) and includes a receiver 120, a retainingand articulating structure or collar 140, and a cradle 160. The receiver120 has a generally U-shaped appearance with a generally cylindricalinner profile and a faceted outer profile. A base 126, with a pair ofupstanding arms 129 forms a U-shaped cradle which define U-shapedopenings 127 through the faceted sides of the receiver 120.Alternatively, receiver 120 may be provided with openings having any ofa variety of shapes and dimensions depending, in part, on the size andshape of the rod to be received.

Both arms 129 have at least one helical wound guide and advancementstructure 125 at least partially situated along their internal wallsbeginning from the top surface 128 end of the receiver 120. The guideand advancement structure 125 of the receiver 120 are configured to matewith at least one exterior helically-wound guide and advancementstructure of a closure structure (not shown in this embodiment), whichassist in preventing the arms from spreading open. The closure structure13 described in the anchor assembly 10 may be used with anchor assembly110 to secure a portion of a rod within a receiver assembly 112. Again,it should be appreciated that while the closure structure 13 shown maybe preferred, closure structures utilizing a number of other suitablestructures and features may be utilized without departing from the scopeof this invention.

The outer surface of the receiver 120 includes tooling attachmentfeatures, such as grip bores 121, on the outer surface of both arms 129.Grip bores 121 function, for example, to allow a variety of tools toengage the receiver assembly 112 for subsequent implantation andpositioning of the receiver assembly 112 and spinal anchor assembly 100.Additional features of the receiver 120 include two steps 138 extendinginwardly from the inside walls of the arms 129 (with one step 138situated on each arm 129). By way of example only, each step 138 spansat least a portion of the inside wall of an arm 129 and is positionedgenerally 180 degrees apart from the other. Located within the base 126end of the receiver 120 is a cavity that is defined by a generallyspherical surface and is sized and shaped for slidable mating andeventual frictional engagement with the retaining and articulatingstructure or collar 140, as described below. Along the walls of thecavity within the base 126 of the receiver is a pair of rounded pivotfeatures 135. The rounded pivot features 135 are located approximately180 degrees apart from one another the wings 147 of the collar 140 andpermit the collar 140 to articulate generally along a single plane.

FIGS. 15-16 illustrate an example of an embodiment of a retaining andarticulating structure or collar 140. The collar 140 is comprised of atop surface 141, a bottom surface 149, an outer convex surface 152, aninner concave surface 145, and a radial protrusion 148. Notably, thecollar 140 is not continuous, and instead includes a slot 144 extendingfrom the top surface 141 to bottom surface 149. The length of the slot144 is dimensioned to be a distance X (best shown in FIG. 16 ) andallows the collar 140 to be temporarily expanded or compressed to securethe collar 140 around the capture structure 160, as described below.

Wings 147 protrude from opposing sides of the outer convex surface 152of the collar 140. The wings 147 and are sized and shaped to mate withthe pivot feature 135 of the receiver 120. By way of example, the wings147 may be D-shaped, but may be any size and shape suitable fordirecting and limiting the pivot direction of the collar 140 (andassociated bone screw 111). When mated, the wings 147 assist in bothpositioning the collar 140 within the receiver 120 and restricting thepivot directions of the collar 140 to along a single plane. The wings147 also restrict relative rotation between the collar 140 and receiver120 along their longitudinal axis. The bone screw 111 and associatedcollar 140 are able to pivot relative to the receiver 120 along a singleplane for subsequent secure positioning and implantation. Interiorprotrusions 108 extend inwardly from opposing sides of the inner concavesurface 145 of the collar 140. The interior protrusions 108 function tomate with the flat surfaces 119 on a capture structure 116 to preventthe rotation of a bone screw 111 relative to the collar 140 along theirlongitudinal axis.

FIGS. 17-18 illustrate an example embodiment of a cradle 160. The cradle160 is comprised of a top surface 167, spherical inner walls 166,concave supports 165, and a base 168. Additional features of the cradle160 include first outer diameter notches 163, second outer diameternotches 191, locking protuberances 190, a central opening 164, lockingledges 162, and tool engaging features 161. As previously noted, thereceiver assembly 112 is typically acquired by a user in an assembledstate. Furthermore, before the cradle 160 is assembled to the receiver120, the collar 140 is first assembled to the receiver 120.

During assembly of the receiver assembly 112, the collar 140 ispositioned within the base of the receiver 120 so that the outer convexsurface 152 rests generally along the spherical cavity located withinthe base 126 of the receiver 120. The collar 140 is positioned withinthe receiver 120 such that the top surface 141 of the collar 140 isfacing the top surface 128 of the receiver 120. Even when the collar 140is in its circumferentially compressed state, the collar 140 cannot exitthe receiver 120 through its central opening 137. Additionally, the pairof wings 147 protruding from the outer convex surface 152 of the collar140 is generally mated with the pair of rounded pivot features 135within the receiver.

As mentioned above, the wings 147 mated with the pivot features 135function to secure the positioning of the collar 140 and permit thecollar 140 to articulate generally along a single plane relative to thereceiver 120.

Once the collar 140 is assembled to the receiver 120, the cradle 160 canthen be placed above the receiver 120 such that the bottom surface 26 ofthe cradle 160 is facing the top surface 28 of the receiver 120. Thecradle 160 is then dropped into the center of the receiver 120 (betweenthe arms 129) until the cradle 160 rests generally circumferentiallywithin the round inner walls of the receiver 120 and the base 168 of thecradle 160 sits on the steps 138. The cradle 160 is then aligned (a toolmay be engaged into the tool engaging features 161 to accomplish this)so that the first outer diameter notches 163 of the cradle 160 arealigned over the steps 138 of the receiver 120. This allows the cradle160 to travel past the steps 138 towards the base 126 of the receiver120 until the base 168 of the locking ledges 162 rest against the insidewall of the receiver 120 and prevent the cradle 160 from travelingfurther down towards the bottom surface 126 end of the receiver 120. Atthis point, the cradle 160 can be rotated along its central axis in theclockwise direction (again, a tool may be engaged into the tool engagingfeatures 161 to accomplish this) so that the locking ledges 162 travelclockwise beneath the steps 138 of the receiver 120. The cradle 160 isrotated clockwise until the steps 138 are forced past the lockingprotuberances 190 of the cradle 160 and the steps 138 are situatedwithin the second outer diameter notches 191. When the steps 138 of thereceiver are situated within the second outer diameter notches 191, thecradle 160 is permanently secured into place and the receiver assembly112 is generally complete (and best shown in FIG. 12 ).

The final step in assembling the spinal anchor assembly 100 duringmanufacturing and before being released for use is assembling the bonescrew 111 to the receiver assembly 112. To accomplish this, a capturestructure 116 of a bone screw 111 is generally concentrically alignedwith the central opening 137 of a receiver. The capture structure 116 isthen passed through the central opening 137 of the receiver 120, whichhas a larger diameter than the capture structure 116.

As the capture structure 116 passes through the central opening 137 itpushes against the bottom surface 149 of the collar 140 until the collar140 is pushing up against the base 168 of the cradle 160. The capturestructure 116 can then advance past the inner chamfer 46 of the collar140 by forcing the collar 140 to increase circumferentially (by furtherlengthening the slot 144) until the largest diameter of the capturestructure 116 passes through the inner protruding ring 151. Once thecapture structure 116 passes through the inner protruding ring 151, thecollar 140 begins to generally return to its original circumference andcapture the capture structure 116 (best shown in FIG. 12 ). Properorientation is ensured such that the interior protrusions 108 are matedwith the flat surfaces 119 on the capture structure 116.

At this point, the connection between the bone screw 111 and receiverassembly 120 resembles a ball-and-socket joint, but with limitedarticulation to only along a single plane. More specifically, thecapture structure 116 is free to articulate along a single planerelative to the collar 140 and the collar is able to articulate along asingle plane relative to the receiver 120. Thus, the collar 140, bonescrew 111 and receiver 120 are able to articulate relative to each otheralong a single plane until they are locked into position. By way ofexample, the bone screw is able to articulate and form an angle betweenits longitudinal axis and the longitudinal axis of the receiver 120 ofapproximately 30 degrees in either direction, for a total of 60 degreesof movement) in the articulating plane.

Therefore, a clinician may configure a spinal fixation system using atleast one spinal anchor assembly 100, at least one additional bone screwassembly (i.e., fixed, provisionally locking, polyaxial), and at leastone rod. The clinician is able to easily align the rod with the receiverassembly 112 of the spinal anchor assembly 100. Additionally, theclinician may leverage the uniplanar screw to direct a correcting forceto the associated vertebra to correct positioning or alignment of thevertebra (e.g., derotation). Thereafter, the closure structure 13 can beengaged to press the rod against the cradle 160, which in turn pressesthe capture structure 116 against collar 140, and the collar 140 againstthe receiver 112. Ultimately, the frictional engagement between theclosure structure 13, rod, cradle 160, capture structure 116, cradle140, and cavity of the receiver 120 are such that the bone screw 111 andreceiver assembly 112 are secured in a desired final position relativeto each other.

FIGS. 19-30 illustrate an example of a spinal anchor assembly 200according to another embodiment of a uniplanar spinal anchor. The spinalanchor assembly 200 includes a bone screw 211, a receiver assembly 212,and a closure structure 13 (shown in FIGS. 5-7 ).

The spinal anchor assembly 200 is preferably composed of a metal (e.g.,titanium, stainless steel, etc.).

The bone screw 211 of the present invention is configured to securelyengage within a bony structure (e.g., pedicle of a vertebra). Thereceiver assembly 212 is able to articulate relative to the bone screw211 along a single plane. This uniplanar engagement between the receiverassembly 212 and the bone screw 211 permits some flexibility forpositioning the rod, while still providing the ability to leverage theanchor assembly 200 to manipulate the vertebra to correct positioningand alignment of the vertebra. By way of example, the anchor assemblymay be implanted such that the articulating plane is the sagittal plane(i.e., movement is cranial-caudal). Positioned as such, force may beapplied to the screw in the transverse plane (i.e., medial/lateraldirection) to derotate a vertebra.

FIG. 21 illustrates an example embodiment of the bone screw 211. Thebone screw 211 of the spinal anchor assembly 200 is comprised of a shank217, a body 208, and a capture structure 216. At least onehelically-wound bone implantable thread 218 extends radially from thebody 208 and functions to secure the placement of the bone screw 211within a bony structure. Additionally, the capture structure 216includes flat surfaces 219 on opposing sides of the capture structure216. The flat surfaces 219 function to assist in restricting therotation between the bone screw 211 and the collar 240 along itslongitudinal axis, as will be discussed in more detail below.

The capture structure 216 includes at least one tool engaging featurethat can be used, for example, to engage and attach various tooling foraligning and advancing the bone screw 211 into a bony structure. Thegenerally spherically-shaped portions 215 of the capture structure 216allow the capture structure 216, for example, to articulate within thecollar 240 along a single plane. The surface of the capture structure216 may be textured (e.g., scored or knurled) for enhancing frictionalengagement with the collar 240, which assists in securing the positionof the bone screw 211 relative to the receiver assembly 212, as will bediscussed in more detail below.

FIGS. 23 and 30 illustrate an example embodiment of a receiver assembly212. The receiver assembly 212 is typically provided in an assembledstate (as shown in FIG. 19 ) and includes a receiver 220, a retainingand articulating structure or collar 240, and a cradle 160. The receiver220 has a generally U-shaped appearance with a generally cylindricalinner profile and a faceted outer profile. A base 226, with a pair ofupstanding arms 229 forms a U-shaped cradle which define U-shapedopenings 227 through the faceted sides of the receiver 220. It will beappreciated however, that receiver 220 may be provided having sideopenings selected from variety of suitable shapes and dimensionsdepending, in part, on the size and shape of the rod to be received.

Both arms 229 have at least one helical wound guide and advancementstructure 225 at least partially situated along their internal wallsbeginning from the top surface 228 end of the receiver 220. The guideand advancement structure 225 of the receiver 220 are configured to matewith at least one exterior helically-wound guide and advancementstructure of a closure structure (not shown in this embodiment), whichassist in preventing the arms from spreading open. The closure structure13 described in the first embodiment may be used with this secondembodiment of the present invention to achieve the securing of at leasta portion of a rod within a receiver assembly 212. Moreover, anyvariation of closure structures may be used to secure at least a portionof a rod within the receiver assembly 212, without departing from thescope of this invention.

The outer surface of the receiver 220 includes tooling attachmentfeatures, such as grip bores 221, on the outer surface of both arms 229.Grip bores 221 function, for example, to allow a variety of tools toengage the receiver assembly 212 for subsequent implantation andpositioning of the receiver assembly 212 and screw assembly 200.Additional features of the receiver 220 include two steps 238 extendinginwardly from the inside walls of the arms 229 (with one step 238situated on each arm 229). By way of example only, each step 238 spansat least a portion of the inside wall of an arm 229 and are positionedgenerally 180 degrees apart from each other. Located within the base 126end of the receiver 120 is a cavity that is defined by a generallyspherical surface and is sized and shaped for slidable mating andeventual frictional engagement with collar 240, as described below.Along the walls of the cavity within the base 226 of the receiver is apair of rounded features 235. The rounded features 235 are locatedapproximately 180 degrees apart from each other and function to securethe positioning of the collar 240.

FIGS. 24-29 illustrate example embodiments of a retaining andarticulating structure or collar 240. The collar 240 is comprised of atop surface 241, a bottom surface 249, an outer convex surface 252, aninner concave surface 245, an interior faceted surface 246, and anexterior faceted surface 248.

In its preferred embodiment, the bone screw 211 may be assembled to thereceiver assembly 212 by passing the distal end of the bone screwthrough the top opening of the receiver 212 and collar 240 (and beforethe cradle is assembled to the receiver 220) until the capture structure216 is resting in the collar 240 (which is resting in the base of thereceiver 220) forming collar assembly 280. In one embodiment of collar240, the inner concave surfaces 245 has helical recesses 247 shaped intosaid inner concave surface 245. Helical recesses 247 facilitate theplacement of the bone screw 211 through the aperture 255 of the collar240. By way of example, helical recesses 247 allow for screws whoseadvancement structure 218 have diameters larger than aperture 255 to beused in bone screw assembly 200. The helical thread 218 of a largediameter bone screw is threaded through helical recesses 247 until shank217 has passed through the aperture 255 of collar 240. Properorientation is ensured such that the interior faceted surface 246 aremated with the flat surfaces 219 on the capture structure 216.

Exterior faceted surfaces 248 are situated on opposing sides of theouter convex surface 252 of the collar 240. Exterior faceted surface 248is sized and shaped to mate with the rounded feature 235 of the receiver220. By way of example, the exterior faceted surfaces 248 may beD-shaped, but may be any size and shape suitable for limiting themovement of the collar 240 (and associated bone screw 211). When mated,the exterior faceted surface 248 assist in positioning the collar 240within the receiver 220. The bone screw 211 is able to pivot relative tothe receiver 220 along a single plane for subsequent secure positioningand implantation, as described above and will be described in moredetail below. Interior faceted surfaces 246 situated inwardly onopposing sides of the inner concave surface 245 of the collar 240. Byway of example, the interior faceted surfaces 246 may be D-shaped, butmay be any size and shape suitable for directing and limiting the pivotdirection of the capture structure 216 (and associated bone screw 211).The interior faceted surfaces 246 function to mate with the flatsurfaces 219 on a capture structure 216 to prevent the rotation of abone screw 211 relative to the collar 240 along their longitudinal axis.

Furthermore, the cradle 260 in the present embodiment is generallyidentical in feature and function as the cradle 60 described in thesecond embodiment, and thus will not be repeated in detail again here.

At this point, the connection between the bone screw 211 and receiverassembly 220 resembles a ball-and-socket joint, but with limitedarticulation in only a single plane. More specifically, the capturestructure 216 is free to articulate along a single plane relative to thecollar 240. The collar 240, bone screw 211 and receiver 220 are able toarticulate relative to each other along a single plane until they arelocked into position, as will be described in detail below. By way ofexample, the bone screw is able to articulate and form an angle betweenits longitudinal axis and the longitudinal axis of the receiver 220 ofapproximately 30 degrees in either direction, for a total of 60 degrees,along the single articulating plane.

Therefore, a clinician may configure a spinal fixation system using atleast one spinal anchor assembly 200, at least one additional bone screwassembly of any variety of constraints (e. g. fixed, provisionallylocking, polyaxial), and at least one rod. The clinician is able toeasily align the rod with the receiver assembly 212 of the spinal anchorassembly 200. Additionally, the clinician may leverage the uniplanarscrew to direct a correcting force to the associated vertebra to correctpositioning or alignment of the vertebra (e.g., derotation). Thereafter,the closure structure 13 can be engaged to press the rod against thecradle 160, which in turn presses the capture structure 216 againstcollar 240, and the collar 240 against the receiver 212. Ultimately, thefrictional engagement between the closure structure 13, rod, cradle 260,capture structure 216, cradle 240, and cavity of the receiver 220 aresuch that the bone screw 111 and receiver assembly 112 are secured in adesired final position relative to each other.

FIGS. 31 and 32 illustrate an example of a spinal anchor assembly 300according to another embodiment of the present invention. The spinalanchor assembly 300 includes a bone screw 311, and a receiver assembly312. The spinal anchor assembly 300 is preferably composed of a metal(e.g., titanium, stainless steel, etc.). The spinal anchor assembly 300may be available to a clinician in a pre-assembled state such that thereceiver assembly 312 is jointly attached to the capture structure 316of the bone screw 311 and has full polyaxial motion. That is, thereceiver assembly 312 and bone screw 311 are able to articulate in alldirections and can ultimately be secured at any number of anglesrelative to each other and in any directions.

When the desired angular orientation is achieved to facilitate rodcapture and the rod is received therein, the receiver assembly 312 islocked into position relative to the bone screw 311. For this to occur,a closure structure 13 is engaged and presses down on the rod whichpresses down on the cradle 360 which presses down on the capturestructure 316. The capture structure presses down on the collet 340 andcollet in turn presses into the receiver 320 which compresses the slot344 and causes the inner spherical surface 349 to frictionally engageand secure the capture structure 316. This permanently fixes theorientation of the receiver 320 relative to the bone screw 311.

The bone screw 311 of the present invention is configured to attachsecurely within a bony structure (e.g., pedicle of a vertebra) with thereceiver assembly 312 assembled to the capture structure 316 of the bonescrew 311. The receiver assembly and bone screw 311 are configured toengage in with full polyaxial motion. This polyaxial engagement betweenthe receiver assembly 312 and bone screw 311 provides for simplifiedpositioning and rod placement. The receiver assembly 312 is configuredto receive a rod and a closure structure 13 secures the rod within thereceiver assembly 312. Once the rod is positioned in the receiverassembly 312 a closure structure 13 will lock the rod in the receiverassembly 312, which also inhibits additional movement between thereceiver assembly 312 and the bone screw 311.

The bone screw 311 of the spinal anchor assembly 300 is comprised of ashank 317, a body 308, and a capture structure 316. At least onehelically-wound bone implantable thread 318 extends radially from thebody 308 and functions to secure the placement of the bone screw 311within a bony structure. The generally spherical shape of the capturestructure 316 allows it, for example, to ultimately be frictionallyengaged with the generally spherical features within the receiverassembly 312. The surface of the capture structure 316 may be textured(e.g., scored or knurled) for enhancing frictional engagement with theretaining and articulating structure or collar 340.

The receiver assembly 312 is typically provided in an assembled stateand includes a receiver 320, a retaining and articulating structure orcollar 340, and a cradle 360. The receiver 320 has a generally U-shapedappearance with a generally cylindrical inner profile and a facetedouter profile. A base 326, with a pair of upstanding arms 329 forms aU-shaped cradle which define U-shaped openings 327 through the facetedsides of the receiver 320. It should be appreciated that side openingsin the receiver may be provided in a variety of suitable shapes anddimensions depending on the size and shape of the rod to be received.Both arms 329 have at least one helically-wound guide and advancementstructure 325 at least partially situated along their internal wallsbeginning from the top surface 328 end of the receiver 320. The guideand advancement structure 325 of the receiver 320 are configured to matewith at least one exterior helically wound guide and advancementstructure 72 of the closure structure 13. Although an embodiment of aclosure structure is described in detail herein, any number of closurestructures may be used without departing from the scope of thisinvention. When the internal and external guide and advancementstructures 325, 72 of the closure structure 13 and receiver 320 areinterlocked, their connection prevents the arms 329 of the receiver 320from spreading open due to the mating features of the guide andadvancement structures 325 and 72. This interlocked configurationprevents splaying of the arms 329.

The outer surface of the receiver 320 includes tooling attachmentfeatures, such as grip bores 321 on the outer surface of both arms 329.These tooling attachment features function, for example, to allow avariety of tools to engage the receiver assembly 312. Additionalfeatures of the receiver 320 include two steps 338 extending inwardlyfrom the inside walls of the arms 329 (with one step 338 situated oneach arm 329). By way of example only, each step 338 spans at least aportion of the inside wall of an arm 329 and are positioned generally180 degrees apart from each other. Located within the base 326 end ofthe receiver 320 is a cavity that is defined by a generally sphericalsurface which is sized and shaped for slidable mating and eventualfrictional engagement with the retaining and articulating structure orcollar 340, as described below.

The collar 340 is comprised of a top surface 341, a bottom surface 349,an outer convex surface 352, an inner concave surface 345, and a radialprotrusion 348. Notably, the collar 340 is not continuous, and insteadincludes a slot (similar to the slot 44 discussed and illustrated in thesecond embodiment of the spinal anchor assembly 300) extending from thetop surface 341 to bottom 342. The slot is dimensioned to be a distanceX and allows the collar 340 to be temporarily expanded or compressed toreceive the capture structure 316 and to secure the collar 340 aroundthe capture structure 316, similar to the collar 40 described above, andthus will not be repeated in detail again here. Furthermore, the cradle360 in the present embodiment is generally identical in feature andfunction as the cradle 60 described in the second embodiment, and thuswill not be repeated in detail again here.

As discussed above, the connection between the bone screw 311 andreceiver assembly 320 resembles a ball-and-socket joint before beinglocked into a configuration. This ball-and-socket characteristic enablesthe receiver assembly 320 to accommodate and capture a rod by rotatingto achieve various angular positions relative to the fixed bone screw311. Therefore, as a clinician configures a spinal fixation system usingat least one polyaxial bone screw assembly 300, at least one additionalbone screw assembly (i.e., fixed, provisional locking, polyaxial), andat least one rod, the clinician is able to easily align the rod with thereceiver assembly 312 of the spinal anchor assembly 300. The steps forlocking in place of the spinal anchor assembly 300 in a desiredposition, in addition to the locking of the spinal anchor assembly 300with the rod(s) are generally the same as the steps detailed in thesecond embodiment of the spinal anchor assembly 200, and thus will notbe repeated here.

FIGS. 33-36 illustrate an example of a spinal anchor assembly 1400according to another embodiment of a provisional locking assembly. Thespinal anchor assembly 1400 includes a bone screw 1410 and a receiverassembly 1412 similar in functions and features to the embodiment of thespinal anchor assembly 10 disclosed herein. Like features and functionswill not be repeated. The spinal anchor assembly 1400 differs from thespinal anchor assembly 10 in that it includes a load ring 1414 engagedwith the collet 1416 (FIGS. 33-34 ).

As shown in FIG. 35 , the load ring 1412 snaps into the collet 1416 andprevents the collet 1416 from compressing on the bone screw 1410 and orcapture structure 13. This allows the polyaxial motion of the bone screw1410 relative to the receiver assembly 1412 to be maintained even afterreduction of the collet 1416 into the receiver 1418. Thus, the collet1416 can become securely engaged (or wedged) into the receiver 1418while the bone screw 1410 is able to still articulate within the collet1416 to provide full polyaxial motion between the bone screw 1410 andreceiver assembly 1412.

When sufficient force is applied onto the load ring 1414, the load ring1414 disengages from the collet 1416 (as shown in FIG. 35 ), thusenabling the collet 1416 to securely engage the capture structure 1420of the bone screw 1410, which inhibits additional movement between thereceiver assembly 1412 and the bone screw 1411.

FIGS. 37-40 illustrate an example of a spinal anchor assembly 1500according to still another embodiment of a provisional locking assembly.The spinal anchor assembly 1500 includes a bone screw 1510 and areceiver assembly 1512 similar in functions and features to theembodiment of the spinal anchor assembly 1410. Like features andfunctions will not be repeated here. The spinal anchor assembly 1500differs from the spinal anchor assembly 10 in that it includes a loadring 1514 and a split ring 1516 (as shown in FIGS. 39-40 ).

The loading ring 1514 snaps into the split ring 1516 and prevents thesplit ring 1516 from compressing on the bone screw 1510 and/or capturestructure 1518 of the bone screw 1510. This allows the polyaxial motionof the bone screw 1510 relative to the receiver assembly 1512 to bemaintained even after reduction of the split ring 1516 into the receiver1520. Thus, the split ring 1516 can become securely engaged (or wedged)into the receiver 1520 while the bone screw 1510 is able to stillarticulate within the split ring 1516.

To lock the receiver assembly 1512 relative to the bone screw 1511,additional force is applied by engaging a capture structure 1518 (orlock screw) into the receiver assembly 1512. As the capture structure1518 is further engaged into the receiver 1514, the bottom surface 71 ofthe closure structure 1518 is forced down upon the spring elements 1522of the loading ring 1514 (best shown in FIGS. 37-38 ). As the springelements 1522 compress, they apply increasing force onto the split ring1516, thus permanently fixing the position of the bone screw 1510relative to the receiver assembly 1512. Furthermore, the bottom surface71 of the capture structure 13 forces down upon the captured rod.Ultimately, the rod 60, receiver assembly 1512, and bone screw 1510 willbe finally fixed relative to each other.

FIGS. 41 and 42 illustrate an example of a spinal anchor assembly 400according to a seventh embodiment. The spinal anchor assembly 400includes a bone screw 411, a receiver assembly 412 having a collar 440and a cradle 460. The spinal anchor assembly 400 is largely similar tothe spinal anchor assembly 300 and like features will not be furtherdescribed herein. The spinal anchor assembly 400 differs from the spinalanchor assembly 300 in that it includes a close-topped receiver assembly412. The close topped receiver assembly 412 includes circular openings427 to receive the rod. The rods slide through the circular shapedopenings 427 and are locked with a closure structure. Any number ofclosure structures (including the closure structure 13 described herein)may be engaged into the receiver assembly 412 to secure the rod. Becausethe receiver assembly 412 is closed, the closure member may preferablybe void of anti-splay features.

FIGS. 43-48 illustrate an example of an arched transverse connector 500according to one example embodiment. The arched transverse connector 500connects two rods that form a part of a spinal fixation assembly (for anexample, refer to FIG. 72 ) situated on either side of the spinalcolumn. The arched transverse connector 500 includes a cross joint 502with an eccentric pin 504, and a pair of connector heads 506 located atthe distal ends of connector arms 508. The eccentric pin 504 in thecross joint 502 enables a user to simply lengthen and shorten thedistance between the arched recesses 510 along the tubular joint collar512. Rotation of the eccentric pin 504 locks and unlocks the cross joint502 to prohibit or allow translation of one connector arm relative tothe other.

The transverse connector 500 is generally arched (as best viewed inFIGS. 43 and 45 ) with the cross connector arms 508 following a radialarc. The generally arched shape of the transverse connector 500 avoidsany unnecessary dural impingement when the arched transverse connector500 is implanted. This is particularly important when the archedtransverse connector 500 is assembled to a posterior spinal fixationassembly. By way of example only, the distance between the center of thearched recesses 510 may range approximately between 25-100 mm (and shownas dimension X in FIG. 45 ). Preferably, the arched transverse connector500 is composed of a metal (e.g., titanium, stainless steel, etc.), butmay also be of a polymer (e.g., poly-ether-ether-ketone (PEEK)) or anyother material suitable for the applications of the present invention.Additionally, the arched transverse connector 500 may be composed of acombination of both metal and polymer materials.

Each connector head 506 includes an eccentric pin 514 that is retainedwithin a cavity 516 of the housing by a retaining c-ring 518. The cavity516 extends generally perpendicular from the front surface 520 of theconnector head 506 to at least partially through the connector head 506.The retaining c-ring 518 engages the circumferential step 522 on theouter surface of the eccentric pin 514 and the annular step 524 withinthe cavity 516, which restricts longitudinal movement of the eccentricpin 514 relative to the cavity 516. The engagement of the retainingc-ring 520 allows rotational movement of the eccentric pin 524 relativeto the cavity 526. A connector head 506 includes an arched recess 520that is shaped and dimensioned to allow the secure placement of a rod(e.g. rod). By way of example, rotation of the eccentric pin 514 securesa portion of a rod within an arched recess, as will be described ingreater detail below.

The surfaces within the arched recesses 510 provide frictionalengagement to a rod when eccentric pins 514 engage the rod along theirengagement surfaces 526. Furthermore, the engagement surface 526 of theeccentric pins 514 and/or the surfaces within the arched recesses 510may have surface features, or surface roughening, to enhance thefrictional engagement between the arched transverse connector 500 androds for enhanced security. By way of example, the eccentric pin 514 isshown as having a generally annular concavity to its engagement surface526 (and best shown in FIG. 48 ). The generally annular concavity allowsfor a greater surface area contact between the eccentric pin 514 and agenerally cylindrical shaped rod. However, the engagement surface 526 ofan eccentric pin 514 may be provided in a variety of shapes anddimensions necessary for providing optimal contact between a variety ofshaped and sized rods, without departing from the scope of thisinvention. For example, pin 504 may be threadably received through anend of the connector arm 508, such that as it is threaded into theconnector arm, it squeezes the cross joint 502 to prohibit translationof the cross arms.

An eccentric pin 514 includes a top surface 528, a bottom surface 530,an engagement surface 526 and a positioning indicator 532. A toolingengaging feature 534 is centrally positioned along the top surface 528,which enables a variety of tools to engage the eccentric pin 514 androtate it along its longitudinal axis (labeled as axis Y in FIG. 48 ).At least one positioning indicator 532 indicates to the user therelative rotational positioning of the eccentric pin 514 relative to theconnector head 506. Additionally, at least one positioning indicator 536may be on the front surface 520 of the connector head 506 to furtherassist the user in properly aligning the eccentric pin 514 relative tothe connector head 506, for example, to securely engage a rod. By way ofexample, if the user aligns the positioning indicators 532, 536 of theeccentric pin and the connector head 506 adjacent to each other, theeccentric pin 514 will be in the appropriate rotational positionrelative to the connector head 506 to securely engage a rod within theadjacent arched recess 510. By way of further example, if the userrotates the eccentric pin 514 approximately 180 degrees from thepreviously described position (such that the positioning indicators 532and 536 are aligned but not adjacent to each other), the eccentric pin512 will be in the appropriate rotational position relative to theconnector head 506 to release or accept a rod within the adjacent archedrecess 510.

FIGS. 46-48 further illustrate the eccentric pin 514, which includes apositional stop 538 and a locking protuberance 540 that radially extendout along a portion of the circumference of the top surface 528. Thelocking protuberance 540 locks the rotational positioning of theeccentric pin 514 once the locking protuberance 540 has passed a headnotch 542 (and best shown in FIG. 44 ). This helps prevent the eccentricpin 514 from unfavorably rotating and releasing the rod from theassociated arched recess 510. The positional stop 538 functions to limitthe rotation of the eccentric pin 514 when the positional stop 538 comesinto contact with the bumper 544.

Furthermore, the eccentric pin 514 includes an annular recess 546centrally located along the longitudinal axis (Y) and adjacent thebottom surface 530 of the eccentric pin 514. The annular recess 546functions to support the positioning of the bottom end of the eccentricpin 516 against the ledge 548 of the connector head 506. Specifically,since the eccentric pin 506 is generally eccentric, the annular recess546 is a non-eccentric feature which maintains the alignment of theeccentric pin 514 within the connector head 506. Upon rotation of theeccentric pin 514 along its central axis within the connector head 506,the eccentric body of the pin acts as a cam and forces the protrudingside of the eccentric pin 515 (relative to its longitudinal axis Y)against a rod captured in the associated arched recess 510.

Assembly of the arched transverse connector 500 to a pair of rods (i.e.,rods) begins with a section of a first rod being captured within anunlocked first arched recess 510 and then a section of a second rod iscaptured within an unlocked second arched recess 510. The archedtransverse connector 500 is then operated by rotating the eccentric pins514 into their locked positions to permanently secure the rods asdescribed above.

FIGS. 49-50 illustrate another example embodiment of an archedtransverse connector 600. The arched transverse connector 600 isassembled during a surgical procedure to two rods and provides supportbetween at least two rods that form a part of a spinal fixation assembly(for an example, refer to FIG. 72 ). The arched transverse connector 600includes an eccentric pin 602, a pair of connector heads 604, andconnector bridge 606.

The transverse connector 600 is generally arched (as best viewed in FIG.50 ) with the center axis of the connector bridge following a radialarc. The generally arched shape of the transverse connector 600 assistsin avoiding any unnecessary dural impingement once the arched transverseconnector 600 is implanted, particularly when the arched transverseconnector 600 is assembled to a posterior spinal fixation assembly.Preferably, the arched transverse connector 600 is composed of a metal(e.g., titanium, stainless steel, etc.), but may also be of a polymer(e.g., poly-ether-ether-ketone (PEEK)) or any other material suitablefor the applications of the present invention. Additionally, the archedtransverse connector 600 may be composed of a combination of both metaland polymer materials.

This embodiment has minimal moving parts so that a clinician mayoptionally perform a minimal amount of adjustments to secure the archedtransverse connector 600 to a pair of rods. Each connector head 604includes an eccentric pin 602 that is retained within a cavity 608 ofthe housing by a retaining c-ring 610. The cavity 610 extends generallyperpendicular from the front surface 612 of the connector head 604 to atleast partially through the connector head 604. The retaining c-ring 610and eccentric pin 623 have essentially the same features and functionsas the retaining c-ring 518 and eccentric pin 514 of the firstembodiment of the arched transverse connector 500, such that theirdescriptions will not be repeated here. Similarly, the connector heads604 (which include, for example, positioning indicators 614 and annularrecess 616) have essentially the same features and functions as theconnector heads 506 of the first embodiment of the arched transverseconnector 500, such that their descriptions will also not be repeatedhere.

FIGS. 51-55 illustrate another example embodiment of an archedtransverse connector 700. The arched transverse connector 700 isassembled during a surgical procedure to two rods (e.g. rods 60) andprovides support between at least two rods that form a part of a spinalfixation assembly (for an example, refer to FIG. 72 ). This embodimentof the arched transverse connector 700 enables the user to configure itin a multitude of configurations so that the arched transverse connector700 may best accommodate the rods that it may attach to. The archedtransverse connector 700 includes set screws 702, a pair of housings704, connector arms 706, and a set of securing blocks 708. The archedtransverse connector 700 has a number of adjustable connections,including; between the two connector arms 708, and between the housings706 and connector arms 708. These adjustable connections enable variousdegrees of movement and linear translation of the arched transverseconnector 700, which will be discussed in more detail below.

The transverse connector 700 is generally arched (as best viewed inFIGS. 51 and 52 ) with the center axis of the connector arms 706following a radial arc. The generally arched shape of the transverseconnector 700 assists in avoiding any unnecessary dural impingement oncethe arched transverse connector 700 is implanted. This is particularlythe case when the arched transverse connector 700 is assembled to aposterior spinal fixation assembly. Preferably, the arched transverseconnector 700 is composed of a metal (e.g., titanium, stainless steel,etc.), but may also be of a polymer (e.g., poly-ether-ether-ketone(PEEK)) or any other material suitable for the applications of thepresent invention. Additionally, the arched transverse connector 700 maybe composed of a combination of both metal and polymer materials.

The housing 704 includes a partially threaded cavity 710 which extendsgenerally at an angle from the front surface 712 of the housing 704 toat least partially through the housing 704. The partially threadedcavity 710 provides at least one internal helical thread 714 for theengaging and advancing a set screw 702 into the housing 704. Theadvancement of the set screw 702 into the housing 704 assists in bindingthe securing block 708 and a rod captured within the arched recess 716of the housing 704, as will be described in greater detail below.

Permanently securing the placement of rods within the arched recesses716 involves further engagement of the set screws 702 into the housings704 and associated securing blocks 708. When a set screw 702 is furtherengaged into a housing 704 and associated securing block 708, thesecuring block 708 binds a number of components within the archedtransverse connector 700. This ultimately results in the secureengagement of a rod within the arched recesses 716 and locking theconfiguration of the arched transverse connector 700, which will bediscussed in more detail below. Although the arched recesses 716 areshown as having an arched profile, any size and shaped recess suitablefor securing any size and shaped rod can be implemented into the housing704 without departing from the scope of the present invention.

At least one exterior helical thread 714 radially extends from the outersurface of the set screw 702 which allows the set screw 702 to engageand advance into the housing 704. Upon advancement of the set screw 702along its central axis into the housing 704 and associated securingblock 708, the securing block becomes bound into the housing 704. Theset screw 702 threadably engages the securing block 708 by way of thethreaded through hole 718 of the securing block 708. If a rod iscaptured within the arched recess 716, the securing block also securesthe rod within the arched recess 716. The securing block includes atongue 720 which at least partially functions to capture and securelyengage a rod within the arched recess when the securing block 708 isbound to the housing 704. Surface features on the engagement surfaces722 of the securing blocks 708 and on the arched recesses 716 may beused to increase the frictional engagement between the securing blocks708, housing 704, and rods.

Engagement of a set screw 702 into the housing 704 and associatedsecuring block 708 also locks the configuration between the housing 704and the adjacent connector arm 706. The distal end of a connector arm706 includes a spherical joint 724 and a keying feature 726. Thespherical joint 724 enables the connector arm 706 to articulate relativeto the housing 704. The keying feature 726 restricts the radialarticulation of the housing 704 relative to the connector arm 706 sothat there is not an unnecessary amount of articulation between theconnector arm 706 and housing 704. By way of example, the housing 704 isable to rotate approximately 20 degrees in both directions relative tothe connector arm 706. The keying feature 726 restricts the rotationalmovement by mating with the key slot 728 in the housing 706, whichprovides limited space for the keying feature 726 to rotate. Thisprovides a user with the ability to make relatively slight configurationadjustments between the housing 706 and connector arm 704, while notmaking the adjustable connection too cumbersome for the user.

The connector arms 706 mate with each other at their medial ends, wherea set screw 702 controls the locked and unlocked configuration betweenthem. Both connector arms have features at their medial ends whichfunction to enable the connector arms 706 to linearly translate relativeto each other as well as slightly angle themselves relative to eachother. The features which function to guide and limit the translationand angulation between the connector arms 706 may be any featurenecessary to enable the configuration between the two connector arms 706without departing from the scope of this invention. By way of example, afirst connector arm may have a threaded hole 732 (shown best in FIG. 53) that enables a connector arm set screw 702 to engage. The looseningand tightening of the set screw 702 would allow the second connector arm706 to linearly translate to either expand or shorten the distancebetween the housings 704. By way of example only, the distance betweenthe center of the arched recesses 716 may range approximately between40-75 mm (and shown as dimension X in FIG. 51 ).

A slot 732 extending across at least part of the second connector arm706 enables the relative linear translation between the two connectorarms 706, while also limiting their linear translation to the confinesof the slot 732. Additionally, the extruded guide 734 assists inmaintaining alignment between the connector arms by mating with the slot732. The extruded guide 734 is not completely circular in cross sectionand, instead, includes flat extensions 736 (best shown in FIG. 54 )which limit the relative angulations between the two connector arms 706.By way of example, the connector arms 706 are able to angleapproximately 15 degrees in either direction about the center axis ofthe threaded hole 730. This provides a user with the ability to makeconfiguration adjustments between the housing 704 and connector arm 706,while not making the adjustable connection too cumbersome for the user.Generally, the medial ends of both of the connector arms 706 haverelatively flat surfaces in order to accommodate smooth lineartranslation between their mating features (i.e., extruded guide 734 andslot 732).

As best shown in FIG. 53 , a split collar 738 is secured around thedistal end of the connector arm 706. The split collar 738 functions toenable the spherical joint 724 to articulate within the spherical socket740 of the securing block 708 while maintaining a secure connectionbetween the connector arm 706 and the housing 704. Flanges 742 radiallyextending from the split collar 738 mate with an annular step 744located in the inside walls of the side through hole 746 of the housing704.

As mentioned above, when the housing set screws 702 are engaged intotheir associated housings 704 and securing blocks 708, the securingblocks 708 ultimately become fixed within the housings 704. When asecuring block 708 becomes fixed within a housing 704, the securingblock 708 also fixes the jointed configuration between the adjacenthousing 704 and connector arm 706. The further engagement of the setscrew 702 into the securing block 708 causes the securing block 708 tobind into the housing cavity 748 which ultimately securely engages thedistal end of the adjacent connector arm 706. Ultimately, the securingblock 708 forces against the distal end of the connector arm 706 (whichpushes the connector arm 706 in a direction away from the housing 704)until the split collar 738 restricts any further movement of theconnector arm 706. The split collar 738 is confined to expanding only tothe size of the annular step 744, which is sized to restrict the splitcollar 738 from expanding enough to allow the distal end of theconnector arm 706 from losing its connection with the housing 704. Byway of example, when the housing set screw 702 is generally fullyengaged within the housing 704 and associated securing block 708, thesecuring block 708 is forcing the permanent fixation of the connectorarm 706 relative to the housing 704. Furthermore, secure fixation of asecuring block 708 within a housing 704 also secures a rod capturedwithin the adjacent arched recess 716, as described above.

FIGS. 56-64 illustrate an example of an embodiment of a reduction tower900. The reduction tower 900 comprises a proximal end 906 and a distalend 907 and includes a housing 901, an interior shaft 902, and agrasping element 910. The housing 901 and interior shaft element 902 areboth hollow to allow the passage of various tooling and/or parts throughtheir centers, generally along their shared longitudinal axis. By way ofexample, a locking tool 1000 (as shown in FIGS. 58 and 59 ) may beinserted through the center of the housing 901 and interior shaft 902and attached at the proximal end of the housing 901 to form a toolingassembly 1100 (as shown by way of example in FIGS. 60-62 ). This toolingassembly 1100 can be used to lock a bone screw assembly configuration(as described herein), and will be discussed in more detail below. Avariety of tooling and parts may be combined with the reduction tower900 to perform a variety of functions, as described below. Furthermore,the reduction tower 900 may also function to lock bone screwconfigurations without the addition of accessory tooling (i.e. lockingtool 1000), which will also be discussed in more detail below.

The grasping element 910 of the reduction tower 900 includes a springelement 920, a finger grip 911, a latch 921, and a grasping arm 922.Grasping features 904 are located at the distal end of the grasping arm922 and housing 901 and function to engage, for example, the receiver 20(of receiver assembly 12) of an anchor assembly 10. One advantageous useof the reduction tower 900 is the ability to lock any of the provisionallocking screws without using a closure structure.

As described above, when the bone screw assembly 10 is secured to a bonystructure in its unlocked position, the receiver assembly 12 canarticulate freely relative to the bone screw 11. After determining thenecessary orientation of the receiver assembly 12 relative to the bonescrew 11 to receive the rod and positioning the rod in the receiver, theclinician may use the reduction tower 900 to provisionally lock the bonescrew assembly 10 orientation without using a closure member.

To provisionally lock the bone screw assembly 10, for example, theclinician positions the open (unlocked) distal end 907 of the reductiontower 900 adjacent and generally concentric to the receiver assembly 12of the spinal anchor assembly 10. The user then advances the distal end907 of the reduction tower 900 over at least a portion of the receiverassembly 12 and generally aligns the grasping features 904 of thereduction tower 900 with the tool engaging features (i.e., grip bores21) of the receiver 20. The clinician then locks the reduction tower 900by compressing the grasping element 910 towards the housing 901, forexample, by pressing on the grasping arm 922 until the latch 921 engagesthe latch keeper 930. When the latch 921 is fully engaged with the latchkeeper 930, the grasping features 904 can fully engage the tool engagingfeatures of the receiver 20 (as illustrated in FIGS. 58 and 59 ), thussecuring the receiver 20 within the distal end 907 of the reductiontower 900.

Once the reduction tower 900 is securely mated to the receiver assembly12 of a spinal anchor 10, the interior shaft 902 can be advanced in thedirection of the distal end 907 of the reduction tower 900. This can beaccomplished in a number of different ways, such as, for example, byattaching a T-handle or a torquing tool (not shown) to the proximal endof the interior shaft 902 and forcing the interior shaft 902 to rotatealong its longitudinal axis. At least a portion of the interior shafthas exterior threads 923 that engage interior threads 925 along at leasta portion of the interior wall of the housing 901 (and best shown inFIG. 62 ). This threaded engagement allows the interior shaft 902 totranslate along its longitudinal axis relative to the housing 901 whenthe interior shaft 902 is rotated in either direction.

As depicted in FIGS. 63-64 , in order to lock the configuration of thespinal anchor assembly 10, the interior shaft 902 is advanced in thedirection of the distal end 907 of the reduction tower 900. The interiorshaft 902 is advanced until the distal end of the interior shaft 902 isforcing down upon the rod (such as a rod 60) captured within thereceiver assembly 12 (and best shown in FIGS. 63 and 64 ). The distalend of the interior shaft 902 continues to force down upon the rod untilthe collet 40 has securely wedged itself into the receiver 20 such thatthe bone screw 11, collet 40 and receiver 20 are no longer able to moveindependently of each other. As described above, when the collet 40becomes securely wedged into the receiver 20, the collet 40 compressesand secures the capture structure 16 of the bone screw 11 within itsinterior spherical surface 49. By way of example, a feature within thereduction tower 900 may produce an audible indicator (i.e., a clickingsound) once the interior shaft 902 has advanced the necessary distanceto lock the configuration of the spinal anchor assembly 10. Any numberof different mechanisms or features (i.e., visual markers, break-awaytorquing tool adapters) may be used to indicate to the user that theinterior shaft 902 has advanced far enough so that the spinal anchorassembly 10 is now locked into its configuration, without departing fromthe scope of the present invention.

Once the interior shaft 902 has advanced the necessary distance to lockthe configuration of the bone screw assembly 10, the user may thenadvance the finger grip 911 to release the latch 921 from the latchkeeper 930, thus unlocking the grasping element 910 and releasing theengagement between the reduction tower 900 and receiver assembly 12. Therod used to lock the configuration of the bone screw assembly 10 canthen be removed from the receiver assembly 12, as necessary, while thespinal anchor assembly 10 remains in the locked configuration. Thisallows the clinician to use the spinal anchor assembly 10, for example,as a tool to assist in positioning the spine (i.e., de-rotation of thespine) and correcting spinal deformities. A rod may be secured withinthe receiver assembly 12 at a later time when the user is prepared tosecure the positioning of the bone screw assembly 10 relative to a rod.

Optionally, and by way of example, a locking tool 1000 may be adapted tothe reduction tower 900 to lock the spinal anchor assembly 10 into adesired configuration. The locking tool 1000 may be used instead of thedistal end of the interior shaft 902 to lock the configuration of thebone screw assembly 10. By way of example, the locking tool 1000 may beadapted to the reduction tower 900 by inserting its distal end into theproximal end 906 of the reduction tower 900 (through the hollow centersof the housing 901 and interior shaft 902). The distal end of thelocking tool 1000 is advanced through the reduction tower 900 until theadapter 1002 of the locking tool 1000 is securely engaged to theproximal end 906 of the reduction tower 900. The adapter 1002 includestwo spring clips 1003 that allow the adapter 1002 to slide over theproximal end of the reduction tower 900 and engage the engaging ends1006 of the spring clips 1003 into the tool locking features 912 at theproximal end of the housing 901. The engaging ends 1006 of the springclips 1003 mate with the tool locking features 912 of the housing 901such that the locking tool 1000 is constrained from movement relative tothe reduction tower 900, both rotationally and along their sharedlongitudinal axis.

Once the locking tool 1000 is securely engaged at the proximal end 906of the reduction tower 900, a torquing tool (not shown), for example,can be adapted to the torque adapter 1004 at the proximal end of thetooling shaft 1005. In order to lock the configuration of the spinalanchor assembly 10, the tooling shaft 1005 is advanced in the directionof the distal end 907 of the reduction tower 900. The tooling shaft 1005is advanced by rotating the tooling shaft (i.e., by rotating the torqueadapter 1004). The locking tool 1000 includes a threaded guide 1010 thatfunctions to assist in the positioning of the tooling shaft 1005. Thetooling shaft 1005 also is partially threaded 1011 along a portion ofits proximal end. Threaded engagement of the threaded guide 1010 withthe tooling shaft 1005 enables the tooling shaft 1005 to linearlytranslate along its longitudinal axis when rotated along itslongitudinal axis.

The tooling shaft 1005 is rotated and advanced toward the spinal anchorassembly 10 until at least a portion of the distal face 1007 is forcingdown upon a rod captured within the receiver assembly 12. The distalface 1007 of the tooling shaft 1005 continues to force down upon the rod(which subsequently forced down upon the collet 40) until the collet 40has securely wedged itself into the receiver 20 such that the bone screw11, collet 40 and receiver 20 are no longer able to move independentlyof each other. Any number of different mechanisms or features (i.e.,visual markers, break-away torquing tool adapters) may be used toindicate to the user that the tooling shaft 1005 has advanced far enoughso that the bone screw assembly 10 is now locked into its configuration,without departing from the scope of the present invention.

Furthermore, the distal end of the locking tool 1000 is shaped anddimensioned such that it may advance into a receiver assembly 12 andlock the configuration of the associated bone screw assembly 10 withouta rod captured within the receiver assembly 12. This is accomplishedgenerally similar to the steps for locking the configuration of the bonescrew assembly 10, as described above, but instead of the distal face1007 of the tooling shaft 1005 forcing down on a rod, the distal face1007 forces down upon generally the top surface 41 of the collet 40. Asdescribed above, the tooling shaft 1005 is advanced until the collet 40is securely wedged within the receiver 20, thus locking theconfiguration of the bone screw assembly 10.

The tooling assembly 1100 may be disassembled by compressing the springclips 1003, thus disengaging the engaging ends 1006 of the spring clips1003 from the locking tool 1000. The locking tool 1000 may be removedfrom the tool locking features 912 at the proximal end of the housing901. This releases the rotational and translational fixation between thelocking tool 1000 and the reduction tower 900 so that the locking tool1000 can slide out and away from the reduction tower 900. The lockingtool 1000 may be assembled to the reduction tower 900 before, during, orafter the reduction tower 900 becomes securely engaged to a receiverassembly 12. Furthermore, the reduction tower 900 may adapt and removeany number of various tooling throughout its use without departing fromthe scope of this invention.

When necessary, the receiver 12 may be released from the distal end 907of the reduction tower 900 by advancing the finger grip 911 towards thedistal end. A spring 931 is housed within the finger grip 911 whichforces the finger grip 911 back to its original position once the useris no longer forcing it towards the distal end of the reduction tower900. Although shown as a spring 931, any number of features may beassociated with the finger grip 911 and/or latch 930 to allow the userto release the grasping element 910 from its locked position, withoutdeparting from the scope of this invention.

The grasping arm 922 is spring loaded by means of a cantilever spring920, but may be spring loaded using any number of elements that forcethe grasping arm 922 back to its original unlocked position. Although acantilever spring 920 is shown in this example, any number of featuresor mechanisms may be used to assist in controlling the movement andplacement of the grasping arm 922 without departing from the scope ofthis invention.

FIGS. 65-66 illustrate an example of a second embodiment of a reductiontower 1200. The reduction tower 1200 includes a housing 1201, aninterior shaft 1202 and a grasping element 1210. This second embodimentof a reduction tower 1200 is essentially the same in features andfunctions as the first embodiment of a reduction tower 900, as describedin detail above. Therefore, a repeated discussion of the similarfeatures and functions of the reduction tower 1200 will not be repeatedhere. However, the reduction tower 1200 presented herein includes arelease button 1203. The release button 1203 functions to position apartially threaded 1204 feature relative to the interior shaft 1202. Thepositioning of the partially threaded 1204 feature enables either aguided or free linear translation of the interior shaft 1202. By way ofexample, engaging the release button 1203 disengages the partiallythreaded 1204 feature from its threaded engagement with the interiorshaft 1202. This enables the interior shaft 1202 to freely and quicklylinearly translate along its longitudinal axis relative to the housing1201. This is desirable for quick positioning of the interior shaft 1202relative to the housing 1201. By way of further example, disengagementof the release button 1203 engages the partially threaded 1204 featureto the exterior threads on the outer wall of the interior shaft 1202.This threaded engagement limits the linear translation of the interiorshaft 1202 relative to the housing 1201 to only when the interior shaft1202 is being rotated along its longitudinal axis.

For instances in which de-rotation of one or more vertebral bodies isdesired, a reduction tower link 1300 is also provided. In accordancewith a preferred embodiment of the present invention, engaging thereduction tower link 1300 to two or more reduction towers 900 allowsderotation of all of the vertebrae together via a ratcheting mechanism.As shown in FIGS. 67-71 , the reduction tower link 1300 includes astationary arm 1302, a moving arm 1304, and a ratchet mechanism 1306.Stationary arm 1302 further comprises a terminal groove 1308 and areceiving aperture 1310 at either end. The terminal grooves 1308 aresized and dimensioned to receive a ratchet pawl 1312. Ratchet pawl 1310is spring-loaded 1328 to engage the moving arm 1304 (or ratchet arm).The aperture 1310 is sized and dimensioned to receive the ratchet post1322 as described below. Additionally, the inner face 1330 of thestationary arm 1302 is comprised of a softer, malleable material(including, but not limited to, silicone) to provide leeway as reductiontower link 1300 interacts with the reduction towers 900.

The moving arm (or ratchet arm) 1304 also contains terminal grooves 1314and a receiving aperture 1316 at either end as well as a malleable innerface 1318. The terminal grooves 1314 which are sized and dimensioned toreceive a final lock nut 1320. As the final lock 1320 is turned, itdraws the ratchet post 1322 through its receiving aperture 1316. Theinner face 1318 is also comprised of a softer, malleable material(including, but not limited to, silicone) to provide leeway as thereduction tower link 1300 interacts with the reduction towers 900.

Ratcheting mechanism 1306 contains an inner ratchet post 1322 and anouter portion comprised of an outer cylinder 1324 and an inner cylinder1326.

As depicted in FIGS. 69 and 71 , squeezing the arms 1302, 1304 togethercauses the ratchet 1306, moving arm 1304, and inner cylinder 1326 tomove towards the stationary arm 1302 as indicated as arrow A. Thespring-loaded ratchet pawl 1312 prevents release of the ratchetingmechanism 1306. The final lock nuts 1320 may be tightened to achievefinal positioning of the reduction tower link 1300. Pushing the ratchetpawl 1312 disengages the spring-loaded mechanism and releases the arms1302, 1304.

According to a second embodiment, instead of a ratcheting mechanism, acam may be used to bring the stationary arm 1302 and moving arm 1304together around the reduction towers 900. A knob on each arm 1302, 1304may be used to adjust the distance between the bars 1302, 1304 inaddition to the travel created by the cams.

An example surgical procedure is described below for use with, forexample, the anchor systems and related tools described herein. Thesurgical procedure described herein is not intended to be exhaustive,such that additional steps that are not discussed herein may beincorporated to the procedure without departing from the intended scope.

The procedure begins, in pertinent part, by placing a spinal anchor(e.g., bone screw 11) into each of a plurality of pedicles. For eachpedicle, the desired entry point is located and the cortex is perforatedusing an awl or burr. Next, a pilot hole is created by passing, forexample, a narrow or lumbar gearshift prove through the pedicle and intothe vertebral body. Care should be taken to ensure the instrument(s) donot breach the cortical wall of the pedicle, as the pilot hole willultimately determine the final position of the screw. The pilot holeshould be inspected for perforations by using a ball-tip probe topalpate the pedicle wall on all sides. Pedicle markers may also beplaced into the pilot holes followed by lateral and anterior-posteriorimaging to verify proper positioning.

In patients with dense bone or where tapping is preferred, depth gaugingmay be accomplished using the markings on the instrument shaft inconjunction with fluoroscopy. If depth gauging is performed, theball-tip probe should again be used to inspect the pilot hole forperforation. After the appropriate screw length is determined, ascrewdriver is used to drive the screw into the pilot hole and advanceit until the desired depth is reached. A screw adjuster may be used ifsubsequent x-ray or fluoroscopy indicate that screw depth adjustment isnecessary.

After the spinal anchors (e.g., bone screw 11) and receiver assemblies(e.g., receiver assembly 12) are secured to the desired pedicles, therods 60 are prepared for placement. The systems described herein includean array of straight and pre-bent (lordosed) rods. Measurements aretaken to determine the appropriate rod lengths using a rod template. Thecorresponding straight or pre-bent rod from the implant tray may then beselected and additional contouring may be performed as needed with anyone of an array of rod benders: (e.g., French benders, in-situ sagittalbenders, in-situ coronal benders, and plate style benders).

A rod holder may then be used to sequentially insert the rod 60 intoeach of the receiver assemblies (e.g., receiver assemblies 12) until therod 60 is lying at the bottom of all of the receiver assemblies 12. Witha portion of a rod 60 fully seated in the receiver assemblies 12,capture structures (e.g., capture structure 16) are engaged into thereceiver assemblies 12. By way of example, the clinician aligns therecessed slot 75 of the closure structure 13 with the recessed slot 24of the receiver (e.g., receiver 20). The alignment of the recessed slots24, 75 prevents incorrect engagement of the interior and exterior guideand advancement structures. Alternately, a lock screw starter guide maybe used to capture the receiver assembly 20 (or closure structure 13)followed by introduction of the lock screw starter.

If the rod 60 is difficult to fully seat in the receiver assembly 120,the rod 60 may be reduced using, for example, a rocker, persuader, orreduction tower 900, 1200. When only a small amount of reduction isrequired, the rocker or the persuader is preferably utilized. Using therocker, the receiver assembly 12 is grasped via the oval grip bores 21on either side of the receiver assembly 20. The rocker may then bedeflected downward until the spinal anchor assembly 10 is levered up andthe rod 60 is fully seated into position within the receiver assembly12. A closure structure 13 may then be inserted using a lock screwstarter. Alternatively, a persuader may be used. To do so, the tip ofthe persuader is slid over the top of the receiver assembly 12. Toreduce the rod 60, downward force is applied to the persuader whilecompressing the handle ratchet closed. Once the rod 60 is fully seatedin the receiver assembly 12, a lock screw starter may be used to placethe closure structure 13. The persuader may be disengaged from thereceiver assembly 12 by releasing the ratchet and pulling up on thepersuader.

A reduction tower 900 is preferably used whenever a large amount ofreduction is required. Prior to using the reduction tower 900, thegrasping element 910 should be in the open position. To use thereduction tower 900, the distal end 907 is placed over the rod 60 andaround the receiver assembly 112 so that the grasping elements 910 reston the capture structure 16 and the oval grip bores 21 are aligned. Thereceiver assembly 112 may be grasped via the grasping features 904 onthe grasping element 910 by slowly closing the grasping element 910towards the housing 901 as described above. With the reduction tower 900securely engaged with the screw 11, the T-handle attached to theproximal end 906 of the reduction tower 900 may be slowly turned untilthe rod 60 is fully seated in the capture structure 16. A lock screwstarter may be used to insert a closure structure 13 through theinterior of the reduction tower 900 to hold the implant 10 in position.Following placement of the closure structure 13, the lock screw startermay be removed, the reduction tower grasping arm 922 may be released andremoved from the spinal anchor assembly 10.

According to one aspect, rod rotation and vertebral derotationtechniques may be utilized to correct coronal and rotary deformities inthe spine. The system of the present invention offers a rod rotationwrench, a reduction tower 900, 1200, and derotation guides (lock screwguides) to perform these operative techniques. In connection with thereduction tower 900, 1200 or a derotation guide, derotation of the spinemay be achieved by using these instruments as an extended moment arm torotate the vertebral bodies in the axial plane.

With the rod 60 fully reduced into the receiver assemblies 12 and theclosure structures 13 are placed loosely, the rod 60 may be rotated intoits desired position. A rod gripper may be placed over the rod 60 andits handle compressed to achieve rigid fixation. Two rod grippers may beused to transform the coronal deformity into kyophosis or lordosiswithin the sagittal plane. After the rod 60 has been rotated into thedesired position, the closure structures 13 may be tightened.

Rods 60 may be rotated using a rod rotation wrench. The rod rotationwrench may be placed over the hex at the end of the rod 60 and rotatedto the desired amount. Vertebral body rotation may be accomplished viathe uniplanar, fixed, or provisional locking screws of the presentinvention. To apply rotational forces to the uniplanar or fixed screws,the lock screw guide is slid over the capture structure 16 of the screw10. The guide may then be moved in the medial-lateral direction torotate the vertebral body in the axial plane.

To apply rotational forces to a provisional locking screw, theprovisional locking screw must first be locked into a fixed position,preferably using the reduction tower 900. To lock the provisionallocking screw, the reduction tower 900 must be rigidly engaged to thecapture structure 16 with the rod 60 fully reduced. To do so, acounter-torque instrument may be slid into the tool locking features 912on the cranial/caudal sides of the reduction tower 900. Next, thelocking tool 1000 is inserted into the center of the reduction tower 900The T-handle attached to the proximal end 906 of the reduction tower 900may be turned in a clockwise direction until the breakaway torque isachieved. The provisional locking tool may be removed as describedabove.

With the provisional locking screw in a fixed position, the reductiontower 900 is leveraged in a medial/lateral direction to rotate thevertebral body in the axial plane. Once the amount of de-rotation isachieved, a closure structure 13 may be inserted (preferably using alock screw starter) and provisionally tightened to hold the rod 60 in afixed orientation. To minimize the chances of pedicle fracture duringvertebral body de-rotation, it is preferable to spread the rotationalforces over a series of adjacent pedicle screws. This is accomplishedvia the reduction tower link 1300 as described above with reference toFIGS. 67-71 .

The reduction tower link 1300 is placed over two or more reductiontowers 900 such that the reduction towers 900 are positioned between theinner face 1312 of the stationary arm 1302 and the inner face 1318 ofthe moving arm 1304. Next, the arms 1302, 1304 are squeezed together viathe ratcheting mechanism 1306 until the desired amount of vertebral bodyde-rotation has been achieved. The final lock nuts 1320 may then betightened to achieve the final positioning of the reduction tower link1300. Pushing the ratchet pawls 1312 disengages the arms 1302, 1304 sothat the reduction tower link 1300 may be removed from the reductiontowers 900.

If compression or distraction is desired, the closure structures 13 onone side of the motion segment should be tightened, leaving the otherclosure structure 13 loose to allow movement along the rod 60. Thecompressor or distractor may be placed over the rod 60 and against thecapture structures 16 of both spinal anchor assemblies 10. With thecompressor or distractor properly engaged, the desired amount ofcompression or distraction may be imparted upon the rods and the secondclosure structure 13 may be provisionally tightened to hold theconstruct in position prior to final tightening of the entire construct.

Once the necessary reduction, de-rotation, compression, and/ordistraction is achieved, the entire construct is tightened. Beginningwith the cephalad screw, the counter-torque is placed over the closurestructure 13 until the slots at the distal end of the instrument arecompletely seated over the rod 60. With a torque T-handle engaged, thelock screw driver is inserted through the counter-torque until it issecurely seated in the closure structure 13. Final tightening may thenbe delivered and these steps may be repeated on the remaining screws.

Next, fixed 600 and adjustable length 500, 700 transverse connectors maybe placed to provide torsional stability to the construct. Theappropriate length transverse connector is determined preferably bymeasuring the distance between the rods 60 using measurement calipers.If necessary, transverse connector benders can be used to make fineadjustments to the length of the fixed transverse connectors 600.

According to the embodiment illustrated in FIG. 23 , eccentric pins 514(locking cams) are used to secure the transverse cross connector 500.Prior to inserting the transverse cross connector 500, the eccentricpins 514 should be in the fully open position. To open them, atransverse connector driver is used to rotate both eccentric pins 514until the positioning indicators 532 are positioned toward the center ofthe transverse cross connector 500.

With the transverse connector holder still attached, the transverseconnector 500 is placed over the rods. Once the connector 500 is seatedon both rods 60, a transverse connector driver is used to turn theeccentric pins 514 180 degrees until the positioning indicators 532 onthe eccentric pins 514 face laterally and align with the positioningindicator 536. The eccentric pins 514 are then fully locked to the rods60.

A distractor may be placed over the transverse connector 500 such thatit engages the medial aspect of the retaining c-ring 518. Final lockingis performed by distracting each ring 518 laterally until it is fullyseated as described above.

While not specifically described above, it will be understood thatvarious other steps may be performed in using and implanting the devicesdisclosed herein, including but not limited to creating an incision in apatient's skin, distracting and retracting tissue to establish anoperative corridor to the surgical target site, advancing the implantthrough the operative corridor to the surgical target site, removinginstrumentation from the operative corridor upon insertion of theimplant, and closing the surgical wound. Furthermore, proceduresdescribed, for example only, may be applied to any region of the spinewithout departing from the scope of the present invention anddimensioning of the implant may be adjusted to accommodate any region.

While this invention has been described in terms of a best mode forachieving this invention's objectives, it will be appreciated by thoseskilled in the art that variations may be accomplished in view of theseteachings without deviating from the spirit or scope of the invention.

Although described with respect to specific examples of the differentembodiments, any feature of the spinal anchor system disclosed herein byway of example only may be applied to any of the embodiments withoutdeparting from the scope of the present invention. Furthermore,procedures described, for example only, involving specific regions ofthe spine (e.g., thoracic and lumbar) may be applied to another regionof the spine without departing from the scope of the present inventionand dimensioning of the implant may be adjusted to accommodate anyregion.

1. (canceled)
 2. An anchor assembly comprising: a bone anchor; and areceiver assembly configured to polyaxially engage with the bone anchor,wherein the receiver assembly comprises: a receiver; and a colletpositioned within the receiver, the collet configured to couple the boneanchor to the receiver.
 3. The anchor assembly of claim 2, wherein thecollet comprises a tapered feature, and the receiver comprises a taperedcavity sized and shaped to slidably mate and frictionally engage withthe tapered feature of the collet.
 4. The anchor assembly of claim 3,wherein the collet further comprises a tooling engagement featureconfigured to engage with a tool to release frictional engagementbetween the tapered feature of the collet and the tapered cavity of thereceiver.
 5. The anchor assembly of claim 2, wherein the colletcomprises a top surface, a bottom surface, an inner surface, and a slotextending along a longitudinal axis of the collet.
 6. The anchorassembly of claim 5, wherein the bone anchor comprises a capturestructure having a convex surface, wherein the convex surface isarticulable on a concave portion of the inner surface of the collet. 7.The anchor assembly of claim 6, wherein the slot is compressible tocause the inner surface of the collet to frictionally engage and securethe capture structure of the bone screw.
 8. The anchor assembly of claim2, wherein the collet comprises a saddle having a contouring surfaceconfigured to receive and mate with a rod within the receiver assembly.9. The anchor assembly of claim 2, wherein the receiver comprises a baseand a pair of arms extending distally from the base.
 10. The anchorassembly of claim 9, wherein each of the pair of arms has an interioradvancement structure situated at least partially along a respectiveinner wall of each of the pair of arms.
 11. The anchor assembly of claim10, wherein the anchor assembly further comprises a closure structurehaving an exterior advancement structure, and wherein the interioradvancement structure of the receiver is configured to mate with theexterior advancement structure of the closure structure.
 12. The anchorassembly of claim 9, wherein each of the pair of the arms comprises asweeping step recessed inwardly from a respective inner wall of each ofthe pair of the arms.
 13. The anchor assembly of claim 12, wherein thecollet further comprises a locking ledge, and the sweeping step isconfigured to guide the locking ledge into position within the receiver.14. The anchor assembly of claim 13, wherein the sweeping step comprisesa notch configured to prevent the locking ledge from backing out of thesweeping step.
 15. The anchor assembly of claim 2, wherein the receiverfurther comprises a tooling attachment feature on an outer surfacethereof, the tooling attachment feature being configured to allow a toolto engage the receiver assembly.
 16. The anchor assembly of claim 2,wherein the anchor assembly further comprises a closure structureconfigured to advance into the receiver and to lock a portion of a rodreceived in the anchor assembly between the closure structure and thecollet.
 17. A method for assembling an anchor assembly in a subject, theanchor assembly comprising a bone anchor and a receiver assemblyincluding a receiver and a collet, wherein the method comprises:coupling the collet with the bone anchor; positioning the collet withinthe receiver; attaching the bone anchor within a bony structure of thesubject; and polyaxially engaging the receiver assembly with the boneanchor.
 18. The method of claim 17, further comprising: articulating thebone anchor relative to the receiver assembly until a desired anglebetween a longitudinal axis of the bone anchor and a longitudinal axisof the receiver is achieved.
 19. The method of claim 18, wherein thebone anchor comprises a capture structure, and the collet comprises aninner surface and a slot extending along a longitudinal axis of thecollet.
 20. The method of claim 19, further comprising: advancing thecollet into the receiver and compressing the slot; frictionally engagingand securing the capture structure with the inner surface of the collet;and locking the receiver assembly relative to the bone anchor.
 21. Themethod of claim 17, wherein the anchor assembly further comprises aclosure structure configured to engage with at least a portion of a rodreceived in the anchor assembly, and the method further comprises:receiving the rod in the anchor assembly; and advancing the closurestructure into the receiver to lock the rod between the closurestructure and the collet.